Miscellaneous documentation fixes

This patch gathers miscellaneous minor fixes to the documentation, and comments
in the source code.

Change-Id: I631e3dda5abafa2d90f464edaee069a1e58b751b
Co-Authored-By: Soby Mathew <soby.mathew@arm.com>
Co-Authored-By: Dan Handley <dan.handley@arm.com>
diff --git a/bl31/aarch64/context.S b/bl31/aarch64/context.S
index 1117026..b127480 100644
--- a/bl31/aarch64/context.S
+++ b/bl31/aarch64/context.S
@@ -207,7 +207,7 @@
 	ret
 
 /* -----------------------------------------------------
- * The followsing function follows the aapcs_64 strictly
+ * The following function follows the aapcs_64 strictly
  * to use x9-x17 (temporary caller-saved registers
  * according to AArch64 PCS) to save floating point
  * register context. It assumes that 'x0' is pointing to